a = int(input('请输入a：'))
b = int(input('请输入b：'))
c = int(input('请输入c：'))
d = int(b**2 - 4*a*c)
if a == 0:
    print('非一元二次方程')
elif d < 0:
    print('NULL')
else:  
    def f(a,b,c):         
        x1 = (-b + pow(d,0.5)) / (2*a)
        x2 = (-b - pow(d,0.5)) / (2*a)
        return x1,x2
    print('方程的解是',f(a,b,c))    